Detergent compositions comprise surfactants for cleaning soils from fabrics and other surfaces. A variety of surfactants exist. However a particularly preferred anionic surfactant is linear alkyl benzene sulphonate (LAS). LAS is a preferred surfactant since it provides superior cleaning and detergency power.
Linear alkylbenzene is typically manufactured on an industrial scale using one of three commercial processes which differ from one another primarily by virtue of the catalyst system employed. One process employs an aluminum trichloride catalyst, another process uses a hydrogen fluoride catalyst, while the third process uses solid alkylation catalyst, known as DETAL™. The three processes result in linear alkylbenzene products with different phenyl isomer distributions. The process for making LAS using the DETAL™ catalyst (UOP, LLC, Des Plaines, Ill.) as taught by Huntsman in U.S. Pat. No. 6,849,588 or US 2003/0096726A1, results in LAS products with a high percentage of the 2-phenyl isomer.
A typical phenyl isomer distribution for products of the hydrogen fluoride process is about 16% to 18% 2-phenyl isomer. By contrast the typical 2-phenyl isomer content of LAS made using the DETAL™ catalyst is higher, generally greater than 20%. This LAS species is often referred to as “high 2-phenyl” linear alkylbenzene, whereas the product of the hydrogen fluoride process, which is relatively low in 2-phenyl isomer content, is often referred to as “low 2-phenyl” linear alkylbenzene.
The benefits of using DETAL™ prepared LAS include the safety of the production process and improved detergency performance of the LAS.
The Applicant has found however that when formulating a detergent composition with the DETAL™ LAS, the composition freezes at a higher temperature as compared to when formulating with LAS produced using the HF catalyst. In some instances the composition has in fact frozen at temperatures as high as 10° C. The freezing of the composition is particularly noticeable when the composition is transparent and the frozen composition turns opaque. Moreover this phenomenon also leads to dissolution and performance issues, as the product cools and becomes more viscous. This phenomenon is more prevalent when the content of the 2 phenyl isomer of LAS is increased since the Krafft temperature of the surfactant system increases with increasing 2-phenyl isomer content.
The Applicant has therefore set out to find a solution to this problem of early freezing of the composition.